Sewing machine presser devices



Nov. 12, 196s E. H. DQERNER 3,410,239

SEWING MACHINE PRESSER DEVI-CES Filed Oct. 30. 1967 F WIW INVENTOR. E rnesr H. Doerner A TORNEY United States Patent O 3,410,239 SEWING MACHINE PRESSER DEVICES Ernest H. Doemer, Montvale, NJ., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Oct. 30, 1967, Ser. No. 678,884 6 Claims. (Cl. 112-235) ABSTRACT OF THE DISCLOSURE An improved presser device including a metallic coil compression spring completely embedded in a resilient material and interposed between a presser bar carrying a presser foot and means for changing pressure exerted by the presser foot against a feed dog. The foregoing combination dampens vibrations of the presser foot induced by repeated hammerings of the feed dog in its successive feed lift motions,

BACKGROUND OF THE INVENTION Field of the invention The invention relates to sewing machine presser devices.

Description of the prior art Heretofore, sewing machine presser devices have generally included a metallic spring interposed between a presser bar carrying a presser foot and means for changing pressure exerted by the presser foot against a feed dog. The foregoing arrangement, has often proven to be less than optimal because repeated hammering of the feed dog in its successive feed lift motions sets up vibration in the presser foot system and, metallic springs, rather than absorbing this energy, tend to aggravate vibrations. The vibrations of the presser foot cause poor feeding of work fabric sandwiched between the presser foot and the feed dog because the presser foot is only erratically in contact with the feed dog and then with varying degrees of pressure. Increasing the pressure of the presser foot can result in marking of the work fabric.

Summary of the invention It is, therefore, a primary object of the invention to provide an improved sewing machine presser device in which vibrations set up in a presser foot by repeated hammering of a feed dog in its successive feed lift motions are effectively dampened.

Other objects and a fuller understanding of the invention can be had by referring to the description and claims taken in conjunction with accompanying drawings.

Brief description of the drawings FIG. 1 is a head end elevational view of a sewing machine with the face plate removed to show the improved presser device and,

FIG. 2 is a perspective longitudinal sectional view of a metallic coil compression spring embedded in a resilient material.

Description of the preferred embodiment With reference to the drawings, the improved presser device is illustrated incorporated in a sewing machine having a frame including a work supporting bed 11 and a sewing head 12 overhanging the work supporting bed.

Mounted in the bed is a four motion feed dog 13 having feed teeth 14. Feed lift, advance, drop and return motions may be imparted to the feed dog by any conventional work feed actuating mechanism. An example of such "ice work feed actuating mechanism is shown, for example, in United States Patent No. 2,075,598, March 30, 1937, Zonis, to which reference may be had.

Mounted in a bushing 15 in the sewing head is a presser bar 16 having a coaxial bore 17 in the vtop portion A presser foot 18 is connected to the bottom portion of the presser bar by a thumbscrew 19. The presser foot has ai sole plate 20 which contacts the feed teeth of the feed A collar 21 is connected to the top portion of the presser bar by a set screw 22. The presser foot is raised by a conventional presser lifter indicated generally at 23 through a link 24 which is connected to the presser lifter and bears against the bottom ofthe collar 21 on the presser bar.

Mounted in a tapped hole 25 in the top of the sewing head coaxial with the presser bar is a thumbscrew 26 for changing pressure exerted by the sole plate of the presser foot against the feed teeth of the feed dog. The thumbscrew includes a knurled knob 27 at the top for turning the thumbscrew and a threaded portion 28 which seats in the tapped hole 25 in the sewing head.

Extending downwardly from the threaded portion 28 is a rod 29 which may be formed as an integral part of the threaded portion or made separately and rigidly secured thereto. At the free lower extremity 30 the rod 29 is formed of reduced diameter, the reduced diameter portion 30 forming a shoulder 31 where it joins the rod 29. The lower extremity 30 of the rod 29 extends part way into the coaxial bore 17 in the top portion of the presser bar leaving an annular space 33 between the rod portion 30` and the coaxial bore 17.

Mounted on the lower extremity 30 of the downwardly extending rod 29 are a washer 34 which abuts the shoulder 31 which is formed between the rod portions 29 and 33, a metallic coil compression spring 35 which is completely embedded in a resilient material 36 forming an embedded coil compression spring 37 which abuts the washer 34, and a second washer 38 which is sandwiched between the embedded coil compression spring 37 and the top of the presser bar 16 and has a coaxial pilot portion 39 which seats in the annular space 33 which is formed between the lower extremity 30 of the downwardly extending rod and the coaxial bore 17 in the top portion of the presser bar.

A metallic coil compression spring 35 which has been found to work well is composed of steel wire having a diameter of approximately 0.05 of an inch. The outer diameter of the coil compression spring is approximately 0.365 of an inch. There are 16 active coils over a length of approximately 2.25 inches.

A resilient material 36 which has been found to work well is composed of urethane elastomer. An elastomer is defined as a material which at room temperature can be stretched repeatedly to at least twice its original length and immediately upon release of the strain will return with force to its approximate original length. The resilient material 36 has an inner diameter of approximately 0.2 of an inch, an outer diameter of approximately '0.5 of an inch, and a length of approximately 2.25 inches. The resilient material is molded around the coil compression spring 35 and completely embeds Athe spring. There is no adhesive bond between the coil compression spring and the resilient material. Since, for urethane elastomer, an increase in temperature causes a decrease in dampening ability, thin sections are used to dissipate heat.

Various properties of a urethane elastomer which have been found to work well are as follows. The `impact resilience as measured by a Bashore Resiliometer is approximately 34 percent. The hardness as measured by a Durometer is between 25 and 40. The compression set is approximately 8.9 percent. The compression strength at 5 percent deilection is approximately 9.8 p.s.i.; at 10 percent, 21 p.s.i.; at 15 percent, 33.1 p.s.i.; and at 20 percent, 46.8 p.s.i. The tensile strength is approximately 1000 p.s.i. and the elongation at break is approximately 750 percent. The tensile modulus at 100 percent elongation is approximately 50 p.s.i. and at 300 percent elongation 90 p.s.i. The tear strength is between 30 and 35 pounds per linear inch. Although some of the foregoing properties are not necessary for proper performance of the urethane elastomer, they are useful as a control for the elastomeric compounding process. Performance of the urethane elastomer is significantly aifected by the accuracy of the elastomeric compounding process.

In operation, vibrations set up in the presser foot 18 by repeated hammerings of the feed teeth of the feed dog 13 against the sole plate of the presser foot are effectively dampened by the coil compression spring 3S embedded in the resilient material 36 of urethane elastomer. The energy absorption or dampening ability of the embedded coil compression spring 37 is approximately twice that of a coil compression spring 35 operating alone. The depth of the bore 17 in the top portion of the presser bar 16 provides clearance for the lower extremity 30 of the downwardly extending rod for adjustment of the presser foot pressure by the thumbscrew 26 and during upward and downward movement of the presser bar.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made by Way of example and that numerous changes in the details of construction and the cornbination and arrangement of parts can be resorted to without departing from the spirit and the scope of the invention.

Having thus set forth the nature of the invention, what is claimed is:

1. An improved presser device for a sewing machine having a frame, a four motion feed dog mounted in the frame, means for imparting feed lift, advance, drop and return motions cyclically to the feed dog, a presser bar carrying a presser foot mounted in the frame with the presser foot in opposition to the -feed dog, and means mounted in the frame for changing pressure exerted by the presser foot against the feed dog, said improved presser device comprising a metallic spring completely embedded in a resilient material and interposed between the presser bar and said means for changing pressure to dampen vibrations of the presser foot induced by repeated hammerings of the feed dog in its successive feed lift motions.

2. The presser device of claim 1 in which the resilient 4material is composed of urethane elastomer.

3. The presser device of claim 2 in which the metallic spring comprises a coil compression spring composed of steel wire.

4. The presser device of claim 3 in which the diameter of the wire of the coil compression spring is between 0.04 and 0.06 of an inch, the outer diameters of the coil compression spring and the resilient material are between 0.3 and 0.7 of an inch with the coil compression spring completely embedded in the resilient material, the lengths of the coil compression spring and the resilient material are between 1.75 and 2.75 inches with the coil compression spring completely embedded in the resilient material, and the coil compression spring has between 12 and 20 active coils.

5. The presser device of claim 4 in which the impact resilience of the resilient material as measured by a Bashore Resiliometer is between 25 and 45 percent.

6. The presser device of claim 5 in which the hardness of the resilient material as measured by a Durorneter is between 20 and 45.

References Cited UNITED STATES PATENTS 2,616,382 lll/1952 Johnson i12-235 3,089,447 5/1963 Shuman 112-235 3,294,047 12/1966 Graham 112-235 PATRICK D. LAWSON, Primary Examiner. 

